Undersea life support system

ABSTRACT

A life support system for an undersea habitat which derives oxygen and potable water directly from the sea, without connection to shore or supply ships. Dissolved gases including oxygen and nitrogen, are stripped from sea water by passing a stream thereof in counter-current with rising steam derived from sea water heated in the boiler of a rectification tower. Oxygen is then separated from the other desorbed gases and conveyed to the habitat. The exhaust gas from the habitat is passed through a carbon dioxide absorber before being recirculated in the habitat. The carbon dioxide from the absorber and the residue of desorbed gases from the stripper, including nitrogen, are reabsorbed in the sea water, which is ultimately cooled and returned to the ocean.

' United States Patent Halfon [54] UNDERSEA LIFE SUPPORT SYSTEM [72]Inventor: Albert Halfon, Niskayuna, N.Y.

[ 1 Sept. 12, 1972 Primary ExaminerCharles N. Hart Attorney-H. HumeMathews and Edmund W. Bopp [73] Assignee: Air Reduction Company, Incor-57 ABSTRACT porated New York A life support system for an underseahabitat which [22] Filed: April 16, 1970 derives oxygen and potablewater directly from the sea, without connection to shore or supplyships. Dis- [21] Appl' 292l6 solved gases including oxygen and nitrogen,are stripped from sea water by passing a stream thereof in [52] U.S.Cl...55/46, 55/198, 55/68 t urr nt with ng st am'd riv d from sea [51] Int.Cl. ..B0ld 19/00 water heated in the boiler o a fication tower. Ox- 58]Field of Search ..55/68, 69, so, 198, 208, 46; y is then separated fromthe other desorbed gases 203 and conveyed to the habitat. The exhaustgas from the habitat is passed through a carbon dioxide absorber 56 R fd before being recirculated in the habitat. The carbon 1 e erences l edioxide from the absorber and the residue of desorbed UNITED STATESPATENTS gases from the stripper, including nitrogen, are reabh h if t ll d d 3,377,777 4/1968 Isomura ..55/68 Sorbedmthesea waterw 'maeycooereturned to the ocean. 3,369,343 2/1968 Robb ..55/l58 11 Claims, 3Drawing Figures 2 SEAWATER /O ,Ng,CO H20 VAPOR TURBINE 5 /6AS ABSORBER,7/ STRIPPER e RETURN 15a [5 HEAT To SEA BOILER PUMP 6b HABITAT 00 )i as24 2 5 /STALE AIR CLEAN STALE AIR CHILLING UNIT 2 A R 2 1 1 p27 33 al 32WATER s skR Ail N C02 SEPARATOR I9 i I PLANT SCRUBBER 22 TOI 26/ 28:N2)CGOA2S)H2o c0 GAS STORAGE 2 UNDERSEA LIFE SUPPORT SYSTEM BACKGROUNDOF INVENTION This relates in general to techniques and equipment forsupporting human life in an isolated, totally enclosed environment; andmore particularly, to methods and apparatus for supplying lifesupporting gas and potable water to a deep sea habitat.

An application for patent entitled Life Support System Using SolventExtraction is filed at even date herewith by Albert Halfon and Walter S.Moen.

A variety of techniques for life support in an isolated closedenvironment have been developed in the prior art, for such applicationsas space crafts, submarines, and underwater habitats.

In prior art space craft applications, oxygen is usually suppliedinitially to the capsule from a cryogenic source. Exhaust carbon dioxidemay be concentrated by absorption using, for example, lithium hydroxide,silica-gel molecular sieves, or monoethanolamine. Oxygen may bereclaimed from the desorbed carbon dioxide by first using hydrogen toconvert it to methane and water, from which the product oxygen'isobtained by electrolysis. In accordance with other methods, oxygen issometimes reclaimed directly from the desorbed carbon dioxide byelectrolysis, leaving free carbon.

In prior art submarine applications, oxygen has been conventionallysupplied by first distilling sea water and electrolysing the distilledwater, returning the hydrogen to the sea. The exhaust carbon dioxide isconventionally disposed of by absorption in a molecular sieve ormonoethanolamine, after which it is pumped back into the sea.

In underwater habitats of the type used in saturation diving programs,the oxygen is conventionally supplied from high pressure storagecylinders outside of the habitat, or by shore-based supplies through anumbilical-type hose. Carbon dioxide is conventionally removed by lime orlithium hydroxide absorption. Another possible prior-art practice hasbeen to use potassium oxide K 0 to both supply oxygen andabsorb carbondioxide. A further prior art alternative has been to use chloratecandles for supplying oxygen.

In accordance with two of the more recent prior art methods for supplyof oxygen and disposal of carbon dioxide to closed underseaenvironments, sea water is used as the working medium. In accordancewith one approach, stale air is pumped out of the undersea chamberthrough a venturi scrubber. This subjects the air to intimate contactwith a fine spray of sea water, causing the oxygen dissolved in the seawater to diffuse into the oxygen-depleted air, and the carbon dioxide tobe absorbed by the sea water, the refreshed air being returned to thechamber. In accordance with another approach, semipermeable membranesare used whereby oxygen and carbon dioxide are exchanged with sea waterby selective diffusion through the membrane.

Each of the aforesaid systems has certain inherent difficulties 'whichwould prevent its adaptation to a large scale undersea installation ofthe type contemplated in connection with the present invention. Forexample, the cryogenic storage of oxygen and lithium hydroxideabsorption of carbon dioxide, such as used in prior art space capsules,would be impractical for undersea installations of the type contemplatedby the present invention because of the logistics required for supplyand storage. Theproduction of oxygen by electrolysis of distilled waterinvolves operational hazards at high pressures. Moreover, the pumping ofcarbon dioxide at high pressure into the sea would cause bubbleformation, which is undesirable in applications where secrecy isdesired. The venturi scrubber technique would necessitate the handlingof very large volumes of sea water to produce the desired supply.

Accordingly, a principal object of the present invention is improvementin techniques and equipment for supplying life supporting gas andpotable water to a closed, isolated environment applicable both to oneatmosphere and hyperbaric environments. A more particular object is toprovide a life support system peculiarly adapted to maintain alarge-scale manned undersea installation having extended working spacesat about atmospheric pressure or above, without the usual umbilicalconnections to ship or shore, or without the generation of tell-taleexhaust bubbles which might give rise to detection.

BRIEF DESCRIPTION OF THE INVENTION These and other objects are realizedin the system of the present invention in which life supporting oxygenand potable water are supplied to a closed, isolated underseaenvironment; and carbon dioxide is eliminated therefrom. This process iscarried out by stripping dissolved gases from sea water by means ofsteam generated by boiling sea water, and separating and condensing thesteam from the desorbed gases for use as potable water. Commerciallypure oxygen for the closed environment is recovered from the desorbedgases; and the waste gases, including waste carbon dioxide derived fromthe closed environment, are ultimately reabsorbed inthe stripped seawater for return to the sea.

The sea water, which is initially at a pressure dependent on the depthof the. sea above the installation floor, is first passed through aturbine to reduce its pressure. It is then heated in several steps ofcountercurrent heat exchange with returning streams of stripped seawater, after which it flows into the top of the gas stripped column inwhich it moves down the column in countercurrent with steam generated byboiling sea water. Dissolved gases, including oxygen, carbon dioxide,and nitrogen, are stripped from the sea water by the steam, passing outthe top of the stripper column. The desorbed gases from the strippercolumn are then passed through means for condensing out the steam, whichprovides potable water for the manned installation. The dried stream ofdesorbed gases then passes to an oxygen separation system, which may beany conventional type of cryogenic system designed to supplycommercially pure oxygen to the installation.

After the stripped sea water flows from the stripper column into theboiler to providesteam, the hot liquid from the boiler passes throughseveral heat exchange steps where it is cooled in countercurrent withthe incoming sea water stream, thus effecting an overall heatconservation for the system. This cooled, stripped'sea water stream thenpasses into an absorber column where waste streams of nitrogen andcarbon dioxide, returning from the system, are absorbed, after which thestream containing the dissolved waste gases is chilled in arefrigeration unit, before return to the sea.

The principal advantages of the processes and systems of the presentinvention are:

1. they provide a substantially self-sufficient, habitable, deep seaenvironment, requiring no connection to ship or shore, except possiblyto a source of power;

2. they combine the function of supplying life supporting oxygen to theundersea habitat with that of supplying potable water, and theelimination of carbon dioxide;

3. they are substantially free from bubbles from exhaust carbon dioxide,which might lead to detection;

4. they make use of the unlimited supplies and sinks available in theopen sea;

5. they employ commercial techniques which have already reached a highdegree of development for other applications; and

6. they provide means for controlling humidity in the habitat, asdesired for comfort, and eliminating contaminants, such as carbonmonoxide and hydrocarbon odors which may be dangerous in a closedsystem.

These and other objects, features, and advantages will be apparent tothose skilled in the art from a study of the detailed specificationhereinafter, with reference to the attached drawings.

SHORT DESCRIPTION OF THE DRAWINGS FIG. 1A is a schematic showing of oneembodiment of a system in accordance with the present invention; and

FIG. 1B is a modification of the system of FIG. 1A in which a single,large air separation plant replaces a smaller air-separation plant incombination with a carbon-dioxide scrubber, as shown in FIG. 1A.

FIG. 2 is a schematic showing of a second embodiment of a system inaccordance with the present invention.

Referring now to FIG. 1A of the drawings, there is shown a schematicflow diagram of the gas and potable water support system of the presentinvention, which is designed to service an extended, manned underseaHabitat 100. It will be assumed, of course, that the system indicated inFIG. 1A is housed inside a multiwalled enclosure of high strength steel,which is suitably built in a manner well known in the art to sustain theundersea pressures at the depth of operation.

Entering the walls of the enclosure is a sea water conduit 1 whichpasses in through a conventional watertight seal. This carries seawater, flowing at the rate which will be discussed hereinafter, and at apressure and temperature dependent upon the depth at which the Habitat100 rests. The stream of sea water in the conduit 1 passes into aconventional turbine 2 which serves to reduce the pressure to a valuewhich exceeds the pressure of one atmosphere, maintained in the Habitat100, by an amount which is equal to the contemplated pressure loss asthe stream passes through the system. From the turbine 2, the sea wasterstream passes at a temperature of, say, 40 F. through column a of afirst heat exchanger 3 which may be, for example, of a conventionalshell-and-tube type, wherein the sea water stream is warmed in acountercurrent heat exchange with a stream of sea water passing throughcolumn b into the absorber 13, from the initial temperature of the oceandepths surrounding the habitat, to a temperature of, say, F. The seawater feed stream then passes into column a of a second heat exchanger 4where it is further heated to a temperature of, say, 62 F. by thecondensation of steam passing from the outlet pipe 18 of the gasstripper 7, and into column b of that heat exchanger in a manner to bedescribed. The output of column a of the second heat exchanger 4 passesinto column a of third heat exchanger 5, where it is further heated to atemperature of, say, 205 F. in an exchange with hot water derived fromthe boiler 8 of the gas stripper 7. This stream then passes through theinlet 6 to a point near the top of the gas stripper column 7. The lattermay be of any of the types of stripping columns well known in the art.

In the gas stripper 7 the stream of sea water then falls down by theforce of gravity in countercurrent with steam rising from the boiler 8,whereupon dissolved gases therein, including oxygen, nitrogen, andcarbon dioxide, are stripped from the falling stream of sea water byrising steam. The latter is generated by means of a heater 9 connectedto a conventional source of power, not shown, which vaporizes the waterin the boiler. The sea water at the bottom of the boiler, which has beenstripped of dissolved gases, then passes out through the outlet 1 1 atapproximately 215 F., flowing into column b of the third heat exchanger5 where it gives up heat to the incoming feed stream, subsequentlypassing into column b of the first heat exchanger 3, where it gives upadditional heat to the incoming feed stream, eventually passing intoabsorber 13 through the inlet pipe 14. The latter may be of any of thetypes well known in the art.

The absorber 13 functions as a reservoir of the stripped sea water intowhich is dissolved the waste gases from the rest of the system, in amanner to be described hereinafter.

Returning now to the gas stripper 7, the output stream of steam,including the gases, which have been stripped from the incoming streamof sea water, flows from the top through the outlet 18 at approximatelythe boiling temperature of water, passing through column b of the secondheat exchanger 4, where the steam is condensed in a heat exchange withthe incoming feedstream. This stream, together with a stream of liquidcondensate from the second heat exchanger 4 then passes through theinlet 19 into the water separator 21. This may take any of the formswell known in the art, such as, for example, a centrifugal rotating drumin which the liquid is collected on the periphery, passing down throughthe outlet 22 to a storage tank of potable water which serves to supportlife in the Habitat 100.

The stream of desorbed gases from which the water has been largelyeliminated, now passes out through the upper outlet 23 and into thejunction 24 where it is joined through conduit 25 by a stream of exhaustair, from the atmosphere of the Habitat 100. The stream of exhaust airfrom the Habitat, together with the fresh stream of desorbed gases, thenpasses through the input 24a of the air separation plant 26. The lattermay be a cryogenic air separation system of any of the types well knownin the art.

The output from the top of the air separation system 26 is commerciallypure oxygen. This oxygen stream flows out through the outlet 27 at aflow rate and temperature which will be discussed presently, and at apressure of substantially one atmosphere in the example underdescription. The remaining gases from the air separation plant, whichinclude nitrogen, carbon dioxide, and a small amount of water vapor,pass in a stream through the conduit 28 to a junction 29. In addition tofresh oxygen from the outlet 27, air, comprising a substantiallyconventional mixture of 21 percent oxygen and 29 percent nitrogen, whichhas been substantially cleansed of carbon dioxide, passes into theHabitat 100 through the outlet 33 of a carbon dioxide scrubber 31, whichreceives, at inlet 32, stale air flowing in from the Habitat 100. Thisexhaust air contains approximately 1% by volume of carbon dioxide. Thescrubber 31, which may be of any of the types well known in the art,eliminates all the carbon dioxide, except between about 0.3 and 0.5percent by volume, which remains in the cleansed stream, passing intothe habitat through the outlet 33. The carbon dioxide residue thenpasses from the scrubber 31 through the outlet 34,and into the junction29 where it becomes part of the stream of waste gases from the system,including nitrogen, carbon dioxide, and water vapor. This stream thenflows through the conduit 35 into the inlet 36 of the absorber column13. Here, these waste gases are reabsorbed into the stripped sea water,which has flowed in through the intake pipe 14. p

The stream of sea water, containing the reabsorbed gases, then passesout through the outlet and through a refrigeration unit 16a which isserviced by a coil 16b which is connected to a refrigeration system 16of any of the types well known in the art, which serves to cool thestream to approximately the temperature of the surrounding sea water.After the stream of sea water, which has reabsorbed the waste gases fromthe system, has been cooled to the desired temperature, it is pumped outby means of the pump 17 to return to the ment, the sea water falling tothe bottom by the force of gravity in a countercurrent exchange withrising steam from the boiler 43a, in which heat is generated by a sea,with which it is integrated without the presence of any tell-talebubbles.

In accordance with a modification of the system of FIG. 1A the sectionto the right of the dotted lines XX is replaced by the section to theright of dotted lines YY, as indicated in FIG. 1B.

In the modified system of FIG. 1B, the stream of desorbed gases fromwater separator 21 passes out through conduit 23 and directly intoHabitat 100'. An air return conduit carries stale air returning from theHabitat 100'. This stream then passes into the air separation plant 26',which is of a type sufficiently large to clean carbon dioxide, watervapor, and hydrocarbons out of the air input from 25'; sending a streamof pure oxygen into the Habitat 100' through conduit 27 this provides abalance between oxygen and nitrogen in the Habitat 100' which is roughlythe same as that in the atmosphere.

Referring now to FIG. 2 of the drawings, there is shown an alternativeimproved system in accordance with the present invention wherein thecarbon dioxide and the other waste gases are all removed in a singlecryogenic gas separation plant. Sea water passes in through a conduit 41and through coil 47a of condenser 47, where it is warmed up in a heatexchange with vapors passing out of the stripping tower 43 throughconduit 44. The warmed input stream then passes into the upper part of astripping tower 43 which is similar to the gas stripper 7 of theprevious embodiheat coil 42 in the manner previously described. Therising steam causes the dissolved gases to be stripped out, and to passout through the upper conduit 44, as in the previous embodiment. Thegas-stripped sea water passes out of the bottom of the boiler 43athrough the conduit 45, from which it passes directly into the top ofthe absorber 46, which functions substantially in the manner previouslydescribed with reference to the absorber 13.

The desorbed gases, together with steam from the stripping tower 43passing out of the upper outlet 44, include oxygen, nitrogen, carbondioxide, and steam. This steam passes through coil 47b of condenser 47where the steam is condensed in a heat exchange with the stream ofincoming sea water in conduit 41, as previously indicated. The stream ofdesorbed gases, from which most of the steam has been condensed, passesthrough the conduit 48 and into the inlet 49 of a water separator 51,which may be of any of the types well known in the art, such as acentrifugal separator. The water collected in separator 51 passes outthrough the lower outlet 51a into the potable water storage, aspreviously described.

The desorbed gases, oxygen, nitrogen, and carbon dioxide, then passthrough conduit 52 leading from the center of the centrifugal separatorand directly into Habitat 200. A stream of recirculated air from Habitat200 passes through the conduit 55 and into the cryogenic gas separationplant 56 which is of a form well known in the art. The cryogenic plant56 is designed to separate out and return to the Habitat 200 through theconduit 57, a supply of commercially pure oxygen. It will be apparentthat the input flow to Habitat 200 through conduits 52 and 57 must equalthe output flow of recirculated air through conduit 55 in order tomaintain the proper oxygen-nitrogen balance in the Habitat 200.

In addition, a stream of high purity nitrogen is separated out in thiscryogenic system, passing out through conduit 58. Part of this streammay be employed to contribute a balance of about 79 percent nitrogen tothe 20 percent oxygen in the simulated air which passes into the habitatthrough conduit 57; or it may be passed through junction 59 to an inertgas storage vessel 61. The remainder of the high purity nitrogen passesout of junction 59 and through the conduit 62 to a junction 63. Here,the stream of waste nitrogen is joined by a stream of additional wastegases, including carbon-dioxide, passing into the junction 63 throughthe conduit 64. The merged waste gas stream then passes through conduit65 and and into the inlet of absorber 46 where it is reabsorbed into thegas-stripped sea water which flows into the absorber through conduit 45.The stream of sea water containing reabsorbed gases then passes outthrough the conduit 66, and ultimately into the sea after optionalcooling, in the manner indicated with reference to the previous figure.

Quantitative values for a specific example employing the system of thepresent invention as derived from the following computations.

CONVENTIONAL U. S. NAVY PRACTICE FOR SUBMARINE ATMOSPHERE TYPICAL DESIGNIN ACCORDANCE WITH PRESENT INVENTION Sea Water Requirement To provide120 standard cubic feet per hour of into Habitat through conduit 57 (seeFIG. 2):

At saturation there are 10' grams 0 per 1 gram of sea water /1 ,000,000

I. At worst condition, 40 percent saturation (4 2. l20 standard cubicfeet per hour 0 10 pounds per hour O Substituting (2) in l 3. Sea waterinput required (into conduit 41) (10 lbs. O,jhr) X (1,000,000 lbs. H O/4lbs. 0

(2,500,000 lbs/hr) 5,000 gallons per minute of sea water. I

Assume difference in temperature between water flowing in and waterflowing out, to be 10 F:

4. Heat required 10 F. X 2,500,000 (lbs./hr.lb.) X

(BTU/F.) 25,000,000 (BTU/hr.)

5. Since 1,000 BTUs are required for 1 pound of steam, then:

25,000,000 (BTU/hr.) produce steam/hr.) I

Converting (BTUs/hr. to kilowatts:

(25,000,000/3,4l2) (BTU/hr.) 7,327 kilowatts.

Cryogenic Plant Requirements Assuming the liquid-to-vapor ratio in thestripping column to be 0.1 then:

6. Flow rate of stripped gas (through conduit 44 at outlet of stripper43) (120/01) 1,200 standard cubic feet per hour.

7. Flow rate for atmospheric recycle (through intake conduit 52 intoseparation plant 56) (assuming 30 percent consumed) 15,000 X (OJ/1.0)10,500 standard cubic feet per hour.

Total flow of air and 0 from cryogenic plant 56 into habitat chamberthrough outlet 57 1,200 plus 10,500 1 1,700 standard cubic feet perhour.

Ratio to 25 ton/day O plant (1 1,700/131,000)

' Power for 25 ton/day cryogenic plant 1,100 kilowatts.

Power for presently disclosed cryogenic plant 56 is roughlyproportional, being 0.0894 X 1,100 100 kilowatts required.

(25 ,000 lbs.

Total power required to operate system, such as disclosed in FIG. 27,327 7,427 kilowatts.

The present invention is not to be construed as limited by the specificcombinations disclosed herein by way of illustration. Moreover, thescope of this invenfion is to be construed only in accordance with theappended claims.

What is claimed is:

1. An undersea system for supplying life supporting fluids includingoxygen to a habitat beneath the sea, and eliminating metabolic carbondioxide from said habitat which comprises in combination:

means for receiving a stream of sea water from the sea surrounding saidhabitat, stripping means including a boiler connected to said receivingmeans for stripping dissolved gases including oxygen, nitrogen andcarbon dioxide from said stream of sea water by contacting said streamof water with steam generated by boiling said stream of sea water insaid boiler, separating means for separating out at least one breathingstream comprising a substantial proportion of oxygen from said strippedgases and supplying said stream of breathing gas to said habitat,

means for continuously removing waste gases including nitrogen andcarbon dioxide from the gas in said habitat, and

means for returning removed waste gases including nitrogen and carbondioxide for reabsorption into the stripped stream of sea water forreturn to the sea.

2. An undersea system for supplying life supporting fluids includingoxygen to a habitat beneath the sea, and eliminating metabolic carbondioxide from said habitat which comprises in combination:

means for receiving a stream of sea water from the sea surrounding saidhabitat,

stripping means connected to said receiving means for strippingdissolved gases including oxygen from said stream of sea water,

separating means for separating out at least one breathing streamcomprising a substantial proportion of oxygen from the balance of saidstripped gases and supplying said stream of breathing gas to saidhabitat,

purifying and absorbing means connected to receive a stream of exhaustgas from said habitat for purifying said exhaust gas and absorbing wastegas including carbon dioxide from said stream of exhaust gas beforereturning said last-named stream to said habitat,

means connected to receive said waste gases from said purifying andabsorbing means and for receiving said stripped sea water from saidstripping means, for reabsorbing said waste gases in said stripped seawater, and

means for returning said sea water stream including I said waste gasesto the sea.

3. An undersea system for supplying life supporting means includingoxygen and drinking water to a habitat beneath the sea which comprisesin combination:

means for continuously deriving a stream of sea water,

an extracting tower including a boiler,

means for introducing said stream of sea water into said tower forcountercurrent exchange with steam rising in said tower from said boilerfor stripping the dissolved gases from said seawater,

a condenser connected to condense the said steam from said strippedgases,

water separation means connected to receive the condensed water vaporand gas from said condenser for separating out and storing condensedwater of potable grade from said stripped gases derived from the top ofsaid tower,

gas separation means connected to continuously receive a stream of airfrom said habitat including the stripped gases from said waterseparation means for separating out separate streams of gas including astream of high purity oxygen from said stripped gases, leaving a residueof waste gases, including carbon dioxide, and to deliver said stream ofoxygen to said habitat,

a final absorbing column connected to receive water from said boiler,and to receive said residue of waste gases including carbon dioxide fromsaid gas separation means for reabsorbing said gas in said water, and

means for returning said water including said absorbed gases to the sea.

4. The combination in accordance with claim 3 including heat exchangermeans connected to warm said incoming stream of sea water ahead of saidextraction tower, said means comprising three heat exchangers,

the first and third of said heat exchangers being warmed by hot waterreturning from the boiler of said extraction tower, and

the second said heat exchanger being warmed by vapor including steamfrom the top of said extraction tower.

5. The combination in accordance with claim 3 wherein said gasseparation means comprises an air separation plant for separating outand delivering to said habitat a stream of high purity oxygen, and

a carbon dioxide scrubber for removing impurities including carbondioxide from a stream of air recirculated through said scrubber fromsaid habitat.

6. The combination in accordance with claim 3 wherein said gasseparation means comprises a single system for receiving recirculatedair from said habitat including the stripped gases from said waterseparation means for separating out a plurality of separate streamsincluding commercially pure oxygen delivered to said habitat, highpurity nitrogen for storage, and waste gas including carbon dioxide.

7. A method for supplying life supporting oxygen to a habitat beneaththe sea and for eliminating metabolic carbon dioxide from said habitatwhich comprises the steps of:

deriving a stream of sea water from the sea surrounding said habitat,

stripping dissolved gases including oxygen, nitrogen and carbon dioxidefrom said stream of sea water by contacting said stream of water withsteam generated by boiling said stream of sea water,

separating out at least one breathing stream comprising a substantialproportion of oxygen from said stripped gases and supplying saidbreathing stream to said habitat,

continuously removing waste gases including nitrogen and carbon dioxidefrom said habitat through purification means, reabsorbing waste gasincluding nitrogen and carbon dioxide into said stream of stripped seawater, and returning said sea water stream including said waste gases tothe sea.

8. A method of supplying life supporting oxygen to a habitat beneath thesea and for eliminating waste gases including metabolic carbon dioxidefrom said habitat which comprises the steps of:

deriving a stream of sea water,

introducing said sea water into an extraction column for stripping saidsea water of dissolved gases, including oxygen, nitrogen, and carbondioxide, by countercurrent exchange with water vapor rising from aboiler in said extraction column,

returning hot water from said boiler into a final absorption column,condensing the water vapor from a stream of stripped gas includingoxygen, nitrogen, carbon dioxide, and water vapor flowing from saidextraction tower and separating out the water from said stream,separating a stream including said stripped gases and exhaust airderived from said habitat into a plurality of streams of which a streamof commercially pure oxygen is directed into said habitat, and at leastone additional stream including waste gases and carbon dioxide arereturned for final reabsorbtion in a stream of water from said boiler,and

returning said stream of water including the reabsorbed waste gases tothe sea.

9. A method in accordance with claim 8,

the steps of warming up the sea water ahead of the stripping step byseparate steps of heat exchange with hot water from the boiler of saidextraction column, and hot vapor including steam from the top of saidextraction column.

10. A method in accordance with claim 8 wherein the said stripped gasesand exhaust air derived from said habitat are separated in a first airseparation step wherein a stream of commercially pure oxygen is directedinto said habitat, leaving a residue stream of waste gases, and in aseparate second step exhaust air from said habitat is continuouslyscrubbed in a carbon dioxide scrubber,

directing a stream of purified air into said habitat and leaving aresidue stream comprising essentially carbon dioxide,

said residue streams of waste gas and carbon dioxide being combined forreturn to the sea in said final reabsorbtion step.

11. A method in accordance with claim 8, wherein said stripped gases andexhaust air from said habitat are separated in a single gas separationsystem from which a stream of commercially pure oxygen is directed intosaid habitat, a stream of high purity nitrogen is at least partiallydirected to storage, and a waste gas stream including carbon dioxide andthe remainder of said nitrogen stream are combined for return for saidfinal absorption step.

2. An undersea system for supplying life supporting fluids includingoxygen to a habitat beneath the sea, and eliminating metabolic carbondioxide from said habitat which comprises in combination: means forreceiving a stream of sea water from the sea surrounding said habitat,stripping means connected to said receiving means for strippingdissolved gases including oxygen from said stream of sea water,separating means for separating out at least one breathing streamcomprising a substantial proportion of oxygen from the balance of saidstripped gases and supplying said stream of breathing gas to saidhabitat, purifying and absorbing means connected to receive a stream ofexhaust gas from said habitat for purifying said exhaust gas andabsorbing waste gas including carbon dioxide from said stream of exhaustgas before returning said last-named stream to said habitat, meansconnected to receive said waste gases from said purifying and absorbingmeans and for receiving said stripped sea water from said strippingmeans, for reabsorbing said waste gases in said stripped sea water, andmeans for returning said sea water stream including said waste gases tothe sea.
 3. An undersea system for supplying life supporting meansincluding oxygen and drinking water to a habitat beneath the sea whichcomprises in combination: means for continuously deriving a stream ofsea water, an extracting tower including a boiler, means for introducingsaid stream of sea water into said tower for countercurrent exchangewith steam rising in said tower from said boiler for stripping thedissolved gases from said seawater, a condenser connected to condensethe said steam from said stripped gases, water separation meansconnected to receive the condensed water vapor and gas from saidcondenser for separating out and storing condensed water of potablegrade from said stripped gases derived from the top of said tower, gasseparation means connected to continuously receive a stream of air fromsaid habitat including the stripped gases from said water separationmeans for separating out separate streams of Gas including a stream ofhigh purity oxygen from said stripped gases, leaving a residue of wastegases, including carbon dioxide, and to deliver said stream of oxygen tosaid habitat, a final absorbing column connected to receive water fromsaid boiler, and to receive said residue of waste gases including carbondioxide from said gas separation means for reabsorbing said gas in saidwater, and means for returning said water including said absorbed gasesto the sea.
 4. The combination in accordance with claim 3 including heatexchanger means connected to warm said incoming stream of sea waterahead of said extraction tower, said means comprising three heatexchangers, the first and third of said heat exchangers being warmed byhot water returning from the boiler of said extraction tower, and thesecond said heat exchanger being warmed by vapor including steam fromthe top of said extraction tower.
 5. The combination in accordance withclaim 3 wherein said gas separation means comprises an air separationplant for separating out and delivering to said habitat a stream of highpurity oxygen, and a carbon dioxide scrubber for removing impuritiesincluding carbon dioxide from a stream of air recirculated through saidscrubber from said habitat.
 6. The combination in accordance with claim3 wherein said gas separation means comprises a single system forreceiving recirculated air from said habitat including the strippedgases from said water separation means for separating out a plurality ofseparate streams including commercially pure oxygen delivered to saidhabitat, high purity nitrogen for storage, and waste gas includingcarbon dioxide.
 7. A method for supplying life supporting oxygen to ahabitat beneath the sea and for eliminating metabolic carbon dioxidefrom said habitat which comprises the steps of: deriving a stream of seawater from the sea surrounding said habitat, stripping dissolved gasesincluding oxygen, nitrogen and carbon dioxide from said stream of seawater by contacting said stream of water with steam generated by boilingsaid stream of sea water, separating out at least one breathing streamcomprising a substantial proportion of oxygen from said stripped gasesand supplying said breathing stream to said habitat, continuouslyremoving waste gases including nitrogen and carbon dioxide from saidhabitat through purification means, reabsorbing waste gas includingnitrogen and carbon dioxide into said stream of stripped sea water, andreturning said sea water stream including said waste gases to the sea.8. A method of supplying life supporting oxygen to a habitat beneath thesea and for eliminating waste gases including metabolic carbon dioxidefrom said habitat which comprises the steps of: deriving a stream of seawater, introducing said sea water into an extraction column forstripping said sea water of dissolved gases, including oxygen, nitrogen,and carbon dioxide, by countercurrent exchange with water vapor risingfrom a boiler in said extraction column, returning hot water from saidboiler into a final absorption column, condensing the water vapor from astream of stripped gas including oxygen, nitrogen, carbon dioxide, andwater vapor flowing from said extraction tower and separating out thewater from said stream, separating a stream including said strippedgases and exhaust air derived from said habitat into a plurality ofstreams of which a stream of commercially pure oxygen is directed intosaid habitat, and at least one additional stream including waste gasesand carbon dioxide are returned for final reabsorbtion in a stream ofwater from said boiler, and returning said stream of water including thereabsorbed waste gases to the sea.
 9. A method in accordance with claim8, the steps of warming up the sea water ahead of the stripping step byseparate steps of heat exchange with hot water from the boiler of saidextraction column, and hot vapor includIng steam from the top of saidextraction column.
 10. A method in accordance with claim 8 wherein thesaid stripped gases and exhaust air derived from said habitat areseparated in a first air separation step wherein a stream ofcommercially pure oxygen is directed into said habitat, leaving aresidue stream of waste gases, and in a separate second step exhaust airfrom said habitat is continuously scrubbed in a carbon dioxide scrubber,directing a stream of purified air into said habitat and leaving aresidue stream comprising essentially carbon dioxide, said residuestreams of waste gas and carbon dioxide being combined for return to thesea in said final reabsorbtion step.
 11. A method in accordance withclaim 8, wherein said stripped gases and exhaust air from said habitatare separated in a single gas separation system from which a stream ofcommercially pure oxygen is directed into said habitat, a stream of highpurity nitrogen is at least partially directed to storage, and a wastegas stream including carbon dioxide and the remainder of said nitrogenstream are combined for return for said final absorption step.